Do you have the Niger Trigger now? I love Triggers and have had several over the years when I had a fish only tank. I've had Niger, Clown and Undulated at various times. Mine would all come to the top of the tank and take food from my fingers whenever I approached the tank. I'm guessing the fish will do fine with each other but one or the other Triggers will eventually eat the shrimp. The last Niger I had lived peacefully in my tank with a Chocolate Chip Star Fish for almost a year. One morning I came down and the starfish was in tiny pieces all over the tank. I think the Triggers get to a certain size or age then the predator in them kicks in. Most reef "clean up crew" like shrimp, crabs, snails, stars are on the Triggers natural diet list. My understanding is they typically don't bother corals.